Ancient fires stoke CRD climate plans

Dr. Kendrick Brown of the Pacific Forestry Centre points to a two-centimetre layer of volcanic ash in a core sample from Begbie Lake. The ash was deposited when Oregon’s Mt. Mazama erupted 7

In the wilderness of a remote South Island lake, Kendrick Brown leans over the boat’s edge and drives a hollow tube into the soft lakebed sediment below.

What he pulls out, one metre at a time, is a historical timeline embedded in layers of organic and non-organic matter. It tells him about the past, and helps paint a picture of what’s to come.

“They’re nature’s archives: stratigraphic sequences in the mud that read like pages in a book,” says Brown, a research scientist with the Canadian Forest Service.

“Basically, the same mud that you sink your toes into during a summer swim is the cover of the book, a recording of history of the region based on the matter that has settled into the lake floor.”

Brown’s project team is based out of the Pacific Forestry Centre in Saanich and includes research technician Nicholas Conder, Nicholas Hebda, and University of Victoria co-op student Kiera Smith. While the focus is on the past, the results can help inform about the future.

The team’s current focus is on sediment cores collected from the Greater Victoria Water Supply Area, namely from Begbie Lake and the Sooke Lake Reservoir.

Brown is examining records from these lakes because paleoclimate indicators suggest the past time interval known as the early Holocene (11,700-7,000 years ago) was warmer and drier compared to present-day.

Scientists hope the data may serve as a first-order reference to what future conditions may be like if induced by climate change.

There are models suggesting temperatures in southern B.C. may increase 2-3 degrees C by 2100, he said.

Extracting pollen and charcoal fragments from the lake sediment cores allows the team to assess how vegetation and fire changed through time,” Brown said.

“We now have a sense of how the fire regime has changed in the Sooke Lake Reservoir catchment throughout the Holocene (period) and will be informing the CRD about the natural variability of fire events within the water supply catchment,” he said. “We’re now working to understand how vegetation in the catchment has changed through time, the signal of which is contained in abundant fossil pollen grains in the sediment.”

The forestry scientists have teamed up with the CRD because the regional body needs to know about fire risk to water supply, Brown said.

“We’re using nature’s archives to learn how the land responded to past changes in climate and identifying past periods that might be analogues for the future,” he said.

Are future generations of South Islanders destined to live in a fire-prone region? Not quite, but fire disturbance may increase in the future.

“We need to plan for and protect against this risk. While fire is not a common form of disturbance today, it was more prevalent in the past,” Brown said.

That plan is still a few years off. The team is hoping to produce an initial report of findings by the end of 2016.

– Brown’s team use a Livingstone corer to reach lake sediment depths of up to 10 metres, sometimes more. The deeper the corer goes, the older the sediment.